Now what!!!

There are plenty of websites, blogs and forums that offer lots of advice for building  a single or fixed speed bike. It seems that most of the forums are populated by people who were born as experts! Whenever someone new comes along to ask for some basic advise it is usually met by calls of 'buy a ready made one and come back when you have learnt something' or 'you have posted this onto the wrong thread this is the metallurgy for hipsters thread.....'. so I have decided to largely ignore such places and find my own way.  
I have a technical background, I have worked in various engineering  type jobs in the past and I know my way around a toolbox so it should be fairly straightforward.....shouldn't it?

Also I am a 42 year old father of two, slightly padded around the framework and a bit grey around the temples so when I go into a cycle shop and I am met by someone wearing a beaney hat in the height of summer who can't look me in the eye during conversation and says 'what you want mate is one of those....' (funny enough the most expensive option) before I've opened my mouth, I kind of get put off going into those shops. There are some very good cycle shops with very good people working in them. If you have one of those near you then use them. Its like a forum but with real people who can interact with other human beings!

So, rant over, where to start indeed.....Firstly terminology.

What is a bottom bracket and is my bottom big enough to require one?
What are dropouts? Are these the people with the beaney hats in the cycle shops?
Spoke nipples? Not going there!

Again I am largely ignoring most of the pseudo technical jargon and sticking with the obvious stuff. Apparently a bottom bracket is the spinney around bit the pedals are fixed to. Right now you know.
Dropouts are where the wheel axles go through. Easy really.
Spoke nipples I think is a medical complaint. I suspect a Google images search would throw up all sorts of possibilities!
To start the build I have been pondering on what bit to do first.
I have reached a decision that the rear wheel would be as good a place as any. This will give me a position for the rear sprocket (the bit at the back where the chain goes over) which in turn will give me a position for the bottom bracket (see above) which will have the crank (the bigger gear with the pedals on) fixed to it. So in theory if these are in line, The chain will run straight.
There is a whole heap of opinion around what size wheels are best and how many teeth the rear sprocket has (keep up) in relation to the crank (I'll be asking questions at the end). Again I'm not going to lose sleep about this yet. As I have a road bike at the moment I will try those wheels on the frame to see if they fit, if so I'll get them then. Easy really. Well in my simple mind it is.......